What is the difference between Intel Pentium D and Intel core 2 duo?

Core 2 duo have better fsb, lower consumption (in Watt), more L2 cache.
But they use the same socket (775) and have 2 cores

Core 2 Duo is the next generation of processors to come out after the Pentium D.

Depending on which one you have Core 2 Duo's can still run games well.

The Core 2 Duo processors are newer and have more advanced technology, and are faster. Both are still fairly outdated now though.

I'm curious too. There are web sites that lay out a table with all chips.
Try www.intel.com and input a question, ie 'comparison of processors'
Hewlett Packard seems to use AMD stuff in their cheaper lines.